This invention relates to improvements in handling seeds and in sowing prepared flats, plug seedling trays, and the like. It has both apparatus and method aspects.
Flats of various sizes may contain various growing media, such as soil, mixtures of sand and peat moss, plastic foam, synthetic growing medium, and so on. For large quantity production of seedlings, there may be several hundred seeds per flat sown at precisely spaced intervals and there may be thousands of flats to be sown. For purposes of this invention the term "flat" is intended to include not only wooden or planter flat boxes filled with growing medium, but also a self-supporting slab of synthetic growing medium such as polyurethane foam, which may have prepared properly spaced-apart indentations for reception of seeds.
Plug seedings are grown in containers which vary considerably in size, partly depending on the plant variety. Individual plastic growing containers or capsules, one for each seedling, are normally assembled into clusters, typically of from fifty to about two hundred. These clusters are typically held in a simple rack of some sort so that the center-to-center spacing and geometry are fixed for a given container type. After the seedling capsules are filled to a desired level with a growing mixture of soil, they pass to a seeding station for reception of seeds, one or more per container, after which the seeds are suitably covered, as with soil or mulch.
Heretofore, many different mechanisms for placing the seeds into flats or capsules have been used, but none has been fully satisfactory. One common seeding device has employed a plate containing a number of shallow pockets having the same configuration and spacing as the rack of capsules or the desired spacing in the flat. The pockets have had a trapdoor type of arrangement at their bottom surface. When the seeding plate has been located properly in relation to the flat or capsules, the trapdoors have been opened and the seeds have fallen by gravity into the flat or capsules beneath the plate. The seed transfer has been acceptable, but there have been problems in getting the proper number of seeds (whether one or more) into each pocket of the seeding plate with sufficient accuracy and speed. Various singulating and distribution devices have been used, but none of these has proved entirely satisfactory to date. The present invention is directed to that problem, as well as others.
Manual sowing or seed distribution has been unable to solve that problem because manual sowing is very slow, is labor intensive, and is subject to human error.
Traditional mechanical and vacuum sowers have possessed major design weaknesses. They have universally required adjustments to compensate for seed shape and size, both types being unduly sensitive to seed geometry. Flat or pointed seeds have been difficult or impossible to sow accurately with vacuum sowers, and inaccuracy has resulted in skipped capsules or in multiples -- two or more seeds in the same locus or pot, necessitating later removal of some seedlings by hand. Devices such as post-pickup shakers and air brushes have been tried and did somewhat reduce the number of multiples, but they did not solve the problem. Mechanical sowers have had similar trouble with seed geometry, particularly with seeds having a flat profile; such seeds have often been physically damaged by a mechanical sower and their germination potential degraded. Small seeds, e.g., those with a diameter less than 2 mm, have caused problems for both mechanical and vacuum sowers. Although it has been possible to improve vacuum sower accuracy by pelletizing small seeds to approximate a spherical shape before sowing, pelletizing has been expensive, and has often had the effect of reducing the percentage of germination.
In our tests, those available prior-art sowers all sowed an excessive number of blanks, usually because small pieces of chaff from the seeds plugged nozzle orifices. Some models cycled low-pressure air behind the nozzles to blow off the chaff, but even though this eliminated some of the chaff, it did not completely solve the problem, for flat-sided chaff still wedged in orifices so tightly that air pressure alone would not remove it.
In summary, although various standard off-the-shelf vacuum and mechanical sowers have been available, none has been found adequate for high-speed accurate sowing.
One object of this invention is to provide a system for positively identifying and sowing each seed as a separate individual, thereby reducing the dependence of sowing accuracy on seed geometry.
Another object is to enable extremely rapid individual sowing to be carried on with very high accuracy.
Another object is to enable multiple sowing when desired and to render this accurate so that the same number of seeds is sowed each time in each capsule or pot or each flat location.
Another object is to provide a versatile sower able to sow many different kinds, types, sizes, shapes, and weights of seeds.